1. Field of the Invention
The present invention pertains to dispensing apparatus for liquid and pulverulent materials, and more particularly to such apparatus which is suitable for a manual or only partially automated dispensing operation. The present invention also pertains to valve sealing or closing apparatus.
2. Description of the Related Art
Many commercially important materials in use today are dispensed in accurate portions accordingly to carefully controlled formulations. Such materials include liquid materials such as food flavorings and chemical additives as well as pulverulent materials such as paints, paint colorants, and inks, for example.
Commercial opportunities have arisen for small quantity, often one-of-a-kind formulation, as well as mass-produced formulations. The assignee of the present invention has provided a number of important advances to promote the art of dispensing relatively small quantities of materials in an accurate, but yet repeatable manner. As with other commercial enterprises, dispensing apparatus must be quickly and easily adaptable to change, especially changes in materials being dispensed, and specific formulations for those materials. As will be discussed further herein, a change common to many types of commercially important materials is that the materials are faster drying, and to be commercially successful, dispensing apparatus must be able to accommodate such fast drying materials.
Broadly speaking, dispensing apparatus used in the food, printing and paint industries, as well as other industries, may be broadly classified as offering either manual or (fully) automatic operation, as well hybrid apparatus performing semi-automatic operation. Examples of manual dispensing apparatus include those disclosed in U.S. Pat. Nos. 4,813,785 and 4,953,985, assigned to the assignee of the present invention. This manual dispensing apparatus has met with immediate commercial acceptance and is valued for its simple operation and low cost of acquisition and maintenance. This dispensing apparatus employs manually operated dispensing pumps of the type disclosed in U.S. Pat. No. 4,027,785, also assigned to the assignee of the present invention.
Depending upon the application, if only a small number of different materials are required, the dispensing pumps and their associated storage canisters may be mounted in a stationary form, with a receptacle for receiving one or more of the materials being passed from one dispensing pump to another. However, when relatively large numbers of different materials are needed for a formulation, the canisters and dispensing pumps are often mounted on a turntable and the receptacle is held stationary while the turntable is rotated to bring a desired material into a dispensing position. For example, to reduce inventory, paint retailers have opted to tint a common paint base with the necessary colorants and additives to provide a desired formulation, on an as-needed demand basis. It is not uncommon for such installations to have a relatively large number of colorants, for example 16 different colorants, for a particular paint "system." The 16 canisters are mounted at the outer periphery of a turntable which is rotated to bring a particular canister into position, with the turntable thereafter being locked in position, while the manual pump dispensers are operated.
U.S. Pat. No. 4,027,785 discloses a so-called dual pump dispenser having a relatively large capacity pump and also a relatively small capacity pump for each colorant, so as to improve dispensing accuracy and speed of delivery. Typically, a partial stroke of the larger size pump may deliver an amount of material equal to several full stroke operations of the smaller size pump.
In each of the above-mentioned dispensing apparatus, a dispensing valve is manually operated which opens a fluid communication path between the pump dispensers and the receptacle to receive the metered material. After dispensing operation, the valve is manually closed to provide a positive closure for the dispensing system, preventing an inadvertent escape of material. Sometimes, the manually operated valve is spring biased to a closed position, requiring an operator to hold the valve open during a pumping operation. Typically, the operator places one hand on the manual valve, and operates the dispensing pumps with the other hand. Depending upon the stroke of the pumps, the condition of their maintenance, nozzle size and viscosity of materials being dispensed, as well as other factors, it may be awkward for an operator to develop the necessary pumping force. Advantages could be attained if the valves were opened and closed at the proper time, without requiring operator intervention.
Also, although a great number of manual pump dispensers have been successful in providing continuous reliable operation over many years, materials having unforeseen rapid drying times are now beginning to be employed and modifications to existing equipment to address these issues are being sought.
In addition to manual dispensing apparatus, the assignee of the present invention has developed (fully) automatic dispensing apparatus, which has also met with ready commercial acceptance. Examples of such apparatus are disclosed in commonly assigned U.S. Pat. Nos. 4,967,938 and 5,078,302. Typically, such apparatus is employed by large volume mass producers of paint, ink and food flavoring materials for example. In this type of apparatus, formulations are stored in a digital computer. Valve operating and pump operating equipment is provided at a dispensing station, located at a point adjacent the turntable, and is coupled to the computer so as to be controlled thereby. An operator selects a particular formula, by name, from a list of formulas stored in the computer. When the formulation is identified, the computer rotates the turntable so as to bring a first material called for by the formula to the dispensing station. The computer then directs the valve operator to open the valve and to prepare the pump operator for a pumping stroke. Under computer control, the pump is operated so as to discharge an amount called for by the selected formula. After the pumping operation is completed, the computer calls for closing of the valve, and the turntable is indexed so as to present the next material called for by the formulation, to the dispensing station, with the dispensing cycle being repeated as many times as necessary. U.S. Pat. No. 5,119,973, also assigned to the assignee of the present invention, discloses what may be termed a "semi-automatic" dispensing apparatus, which is similar to the fully automatic apparatus described above, except that the operator is required to manually index the turntable. As with the fully automatic apparatus, the valve operation and pump operation is under computer control.
As mentioned, the manual dispensing apparatus is attractive to many users because of its low acquisition cost. Modifications to the equipment using computer or analog circuit control of a solenoid actuator or other valve operator would be too costly for this type of product. Accordingly, improvements to this type of dispensing apparatus are still being sought.
The aforementioned U.S. Pat. No. 5,078,302 discloses a sealing valve adapted for retrofit assembly with a fully automatic dispensing apparatus. The sealing valve is spring biased to a closed position, and is held open during a dispensing operation by mechanical linkage attached to the valve operator, which, as mentioned, is under computer control.